An adjustment mechanism for setting the position of a singulator in a seed meter (10). The singulator (30) comprises an arm (32) pivotally mounted about a pivot adjacent a seed disk (18). A shaft (42) with an eccentric connection to a radially outward portion of the arm (32) has a lever (66) pivotally connected on it. The lever (66) has a cam mechanism to displace an actuating sleeve (60) into a resilient sleeve (54) to lock the shaft (42) in a given position when the lever (66) is extending in the direction of the axis of rotation of the shaft (42). When the lever (66) is moved to a right angle orientation the shaft (42) is free to pivot and thus set the position of the arm (32).
